The present invention relates to a method and apparatus for reducing the temperature of a food product, and more particularly when the food product is in the form of a plurality of pieces of the product.
In the food processing industry, it is often desirable that the pieces of food being processed are maintained at a temperature within a few degrees of freezing. Doing so retards the ability of microorganisms and other adverse agents to grow on or in the food product. This is particularly true of raw food products which have not been subjected yet to any processing step, such as meat carcasses (i.e. beef, poultry, and fish) and portions of whole carcasses, as well as fruits and vegetables which have not yet been processed. The fact that the food product has not yet been processed means that there has as yet been no intervening step such as cooking by which microorganisms or other deleterious agents may have been inactivated on or in the product. Thus, treating raw food product is benefited all the more by chilling the food product so as to prevent agents that may already be present from proliferating and thus becoming more able to deleteriously affect the product.
In some processes for processing food, particularly for processing meat, the product may be at ambient temperature or higher (such as in the case of freshly slaughtered meat, or in cases where the meat has been subjected to a processing step involving the application of heat). In these instances as well, it is desirable to chill the meat product to within a few degrees of freezing, and to do so quickly, to achieve the aforementioned objectives of retarding or inactivating deleterious agents.
Meat processors have certain target temperatures for their products that they must obtain in order to meet HACCP requirements. These requirements usually mean that the meat needs to be cooled from between 40xc2x0 F. and 50xc2x0 F. to a final target temperature of 32xc2x0 F. to 36xc2x0 F. for storage or shipping. Further processing plants that receive the raw meat products can demand even tighter temperature controls than those required by HACCP.
Current cooling methods employ manual or semi automatic dispensing of CO2 dry ice nuggets, wet ice or CO2 snow into boxes or carts (known as xe2x80x9ctotesxe2x80x9d) which carry on the order of 2000 pounds of meat at a time. Discretionary cooling of products in this manner can result in widely varying product temperatures with hot spots and/or frozen spots, ultimately resulting in rejected product or excessive cooling costs. In addition, determination of actual product weights may be difficult because of the carryover of wet or dry ice.
In addition to the concerns around achieving the even product temperatures mentioned above, processing plants need to be concerned about the labor involved in the material handling aspects of the current batch process and about the proper exhausting of the sublimated CO2 in the processing room and refrigerated storage areas.
Thus, it is desirable in this industry to provide efficient and rapid processes for cooling food products such as meat carcasses. While some techniques have been disclosed in the prior art, they have yet to achieve an optimum combination of a rapid rate of temperature reduction, a relatively efficient consumption of cryogen used to achieve the temperature reduction, and a rapid rate of throughput in the production of chilled food product. The invention described herein achieves these objectives and others which will be disclosed in the description.
One aspect of the present invention is apparatus for chilling a plurality of pieces of a food product, comprising
(A) cooling means comprising (1) a rotatable drum defining an enclosure and having an inlet for said pieces and an outlet for said pieces, (2) means in said drum for continuously urging pieces in said drum from said inlet through a cooling region in said enclosure and toward and out of the outlet when the drum is rotating, (3) cryogen dispensing means for feeding cryogen from a source outside said drum into said drum and dispensing said cryogen onto said cooling region, and (4) means for rotating said drum;
(B) feeding means for receiving said plurality of pieces and feeding them continuously into the inlet of the rotatable drum, which feeding means includes means for automatically sensing the mass flow rate at which said pieces are being fed into said inlet and for generating electrical signals corresponding to said automatically sensed mass flow rate;
(C) electronic control means for receiving from said feeding means said signals corresponding to said mass flow rate and for receiving electronic inputs corresponding to the temperature of said pieces being fed into said inlet and to the desired temperature of said pieces exiting the outlet of said drum, for preventing flow of cryogen onto said cooling region until a predetermined quantity of said product has been fed into said cooling region, and for automatically controlling the rate at which cryogen is fed by said cryogen dispensing means onto said cooling region as a function of said signal and said inputs so as to dispense cryogen at a rate sufficient to lower the temperature of said pieces to be at the desired exit temperature when they exit the drum;
xe2x80x83wherein when said pieces are fed to said feeding means said feeding means senses the mass flow rate of said pieces and generates and sends to said electronic control means electrical signals corresponding to said mass flow rate, and wherein when the average temperature of said pieces and the desired exit temperature are inputted into said electronic control means, cryogen is dispensed onto said cooling region at a rate sufficient to lower the temperature of said pieces to be at the desired exit temperature when they exit the drum only after a plurality of said pieces occupy said cooling region.
Another aspect of the present invention is a method for cooling a plurality of solid pieces of a foodstuff, comprising
(A) providing a cooling means comprising (1) a rotatable drum defining an enclosure and having an inlet for said pieces and an outlet for said pieces, (2) means in said drum for continuously urging pieces in said drum from said inlet through a cooling region in said enclosure and toward and out of the outlet when the drum is rotating, (3) cryogen dispensing means for feeding cryogen from a source outside said drum into said drum and dispensing said cryogen onto said cooling region, and (4) means for rotating said drum;
(B) providing a feeding means for receiving said plurality of pieces and feeding them continuously into the inlet of the rotatable drum, which feeding means includes means for automatically sensing the mass flow rate at which said pieces are being fed into said inlet and for generating electrical signals corresponding to said automatically sensed mass flow rate;
(C) providing electronic control means for receiving from said feeding means said signals corresponding to said mass flow rate and for receiving electronic inputs corresponding to the temperature of said pieces being fed into said inlet and to the desired temperature of said pieces exiting the outlet of said drum, for preventing flow of cryogen onto said cooling region until a predetermined quantity of said product has been fed into said cooling region, and for automatically controlling the rate at which cryogen is fed by said cryogen dispensing means onto said cooling region as a function of said signal and said inputs so as to dispense cryogen at a rate sufficient to lower the temperature of said pieces to be at the desired exit temperature when they exit the drum;
(D) feeding said pieces to said feeding means whereupon said feeding means senses the mass flow rate of said pieces and generates and sends to said electronic control means electrical signals corresponding to said mass flow rate, inputting into said electronic control means the average temperature of said pieces and the desired exit temperature, and rotating said drum, wherein cryogen is dispensed onto said cooling region only after a plurality of said pieces occupy said cooling region.
A further aspect of the present invention is apparatus for freezing a plurality of pieces of a food product, comprising
(A) freezing means comprising a housing having an inlet for said food product and an outlet for said food product, means in said housing for continuously urging pieces therein from said inlet toward and out of the outlet, and means for supplying cryogen to said housing to freeze product therein by direct or indirect contact with said cryogen;
(B) feeding means for receiving said plurality of pieces and feeding them continuously into the inlet of the housing, which feeding means includes means for automatically sensing the mass flow rate at which said pieces are being fed into said inlet and for generating electrical signals corresponding to said automatically sensed mass flow rate;
(C) electronic control means for receiving from said feeding means said signals corresponding to said mass flow rate and for receiving electronic inputs corresponding to the temperature of said pieces being fed into said inlet and to the desired temperature of said pieces exiting the outlet of said drum, for automatically controlling the rate at which cryogen is fed by said cryogen dispensing means into said housing as a function of said signals and said inputs so as to supply cryogen at a rate sufficient to freeze said pieces in said housing.
Another aspect of the invention is a continuous method for freezing a plurality of solid pieces of a foodstuff, comprising
(A) providing freezing means comprising a housing having an inlet for said food product and an outlet for said food product, means in said housing for continuously urging pieces therein from said inlet toward and out of the outlet, and means for supplying cryogen to said housing to freeze product therein by direct or indirect contact with said cryogen;
(B) providing feeding means for receiving said plurality of pieces and feeding them continuously into the inlet of the housing, which feeding means includes means for automatically sensing the mass flow rate at which said pieces are being fed into said inlet and for generating electrical signals corresponding to said automatically sensed mass flow rate;
(C) providing electronic control means for receiving from said feeding means said signals corresponding to said mass flow rate and for receiving electronic inputs corresponding to the temperature of said pieces being fed into said inlet and to the desired temperature of said pieces exiting the outlet of said drum, for automatically controlling the rate at which cryogen is fed by said cryogen dispensing means into said housing as a function of said signals and said inputs so as to supply cryogen at a rate sufficient to freeze said pieces in said housing; and
(D) feeding said pieces to said feeding means whereupon said feeding means senses the mass flow rate of said pieces and generates and sends to said electronic control means electrical signals corresponding to said mass flow rate, and inputting into said electronic control means the temperature of said pieces and the desired exit temperature, wherein cryogen is provided to said housing sufficient to freeze said product therein.